Ask any frequent traveler, and they’ll tell you that before you rent a car, call your credit card company to find out if they cover insurance. But even that little trick comes with fine print.

Adding a liability waiver to a rental car usually tacks on an additional $10-$20 a day. If you can avoid that, you’re saving significantly.

To activate your credit card’s protection, you have to officially decline the supplemental coverage offered by the rental company and use that credit card to pay for the rental.

Some cards fare better than others: A recent study from CardHub found that Visa ranked the highest in terms of coverage, followed by Discover, American Express, and MasterCard.

So let’s look at some of the fine print. MasterCard won’t cover accidents that take place on dirt or gravel roads. Both Visa and MasterCard require that roads be regularly maintained by the government to fall under their protection. Translation? An accident on a country road or mountain drive could cost you.

You’ve heard me talk about those sneaky “loss-of-use” fees, which is what the rental company charges for every day a car is in the shop. Along with that, you might also be charged administrative fees or a penalty if the car is considered to be devalued.